Bulldozers having a planar, vertically movable blade secured to their forward ends are commonly used in a variety of applications, including (1) ripping, in which a layer of rigid surfacing material is removed from an area, and (2) grading, in which the lower edge of the blade is scraped along a surface. To rip, teeth are used to dig the blade into the surfacing material. Although ripping teeth may be integrally formed with the lower edge of the blade, individual teeth ordinarily are bolted to the lower edge of the blade. These teeth are removable for the scraping operation and are replaceable when broken. Although these teeth have generally proven somewhat satisfactory for a ripping operation, they suffer from a number of serious shortcomings. The principal disadvantage of bulldozer blades having conventional ripping teeth is the relatively large amount of time required to convert from a ripping or brush blade to a scraping blade. During a ripping operation, after the surfacing material has been broken into pieces, the broken pieces must be removed from a surface and the surface leveled. When using conventional ripping teeth, either the teeth must be removed from the blade, a separate grading blade attached to the bulldozer, or a second bulldozer used to grade.
Another problem associated with conventional ripping teeth is their inability to withstand rearward forces without fracturing. The ripping teeth generally project forwardly and downwardly from the lower edge of the bulldozer blade and are thus extremely sturdy in receiving forces from in front of the blade (since these forces act along the axis of the teeth). However, forces imparted to the teeth from a rearward direction, such as when the bulldozer is moving in a reverse direction with the blade down, produce a force transverse to the longitudinal axis of the teeth, which could easily fracture the teeth, thereby necessitating time-consuming and expensive replacement.
In summary, although conventional ripping teeth are generally satisfactory, they require an excessive period of time to convert from a ripping or brush blade to a scraping blade. Also, their design makes them prone to fracture by rearward forces.
Structures devised for pivotally securing a plurality of elongated members (teeth) to a bulldozer blade are illustrated in U.S. Pat. Nos. 2,132,261; 2,262,415; 3,097,439; and 3,595,416. These devices do not easily and quickly convert a conventional blade into a ripping blade. These devices are either too heavy for optimal efficiency or too weak to withstand typically imposed loads. Additionally, these devices lack features which are essential for achieving various advantageous functions. For example, none of the prior art structures includes means for positioning the teeth so that they will not interfere with the use of the blade in grading. Furthermore, some structures, such as that disclosed in U.S. Pat. No. 2,262,415, employ teeth-mounting structures for the teeth which either interfere with use of the blade or are likely to be damaged when the teeth are removed from the blade.